Re: RIP '86 535i B34
Posted: Jul 27, 2017 10:44 PM
Having had mine apart last year I can offer some tips on oil pumps.
To remove the chain the OP Gear must be removed. It is simple enough, just loosen the nut before taking anything else apart.
The oil pump shaft is not the strongest or best made. The shaft is subject to cracking because of the thin metal surrounding the splined drive surface for the gear.
A superior replacement is available. (See reference under NLA parts.) A new gear comes w/ the shaft if you need to change your shaft. Mine broke. If your shaft is good a new sprocket & chain are all you need. DO NOT exceed the torque spec at assembly.
For the price it is not worth taking things apart w/o replacing the OP chain and Sprocket.
The Oil Pump itself:
If the shaft isn't tight, has wear, in the rear half of the pump housing find another pump. It will never develop adequate pressure due to the leakage around the shaft.
Remove and inspect BOTH check balls. Be sure they are clean, round and the springs are not broken/bent.
New gear sets are sometimes available but way too pricy and won't do anything for an otherwise decent pump.
New housings have been NLA for a while. Look for a good used one if a replacement is necessary.
Clear the pick-up screen of all build up. A metal toothbrush (for weld cleanup) works great.
Lap the pump bottom cover flat with a sheet of 360/400 grit wet/dry sandpaper over a sheet of glass/lexan on a suitable bench. Wet it with gas and 20 figure8 strokes will do it.
Do the same with the pump housing. The pump gear end clearance will likely be within spec if the pump is good otherwise. If not a few extra strokes here will fix that. The covers tend to distort between the bolts and leak.
Assembly: pack a slug of chassis grease into the pickup bore to seal it. Pour the pump full of STP and bolt it together. All this is to guarantee that the pump primes immediately and the STP won't run out while you get things put back together. Spin the engine w/ the starter w/ the plugs out until the Oil Pressure Light goes out.
-Dick
To remove the chain the OP Gear must be removed. It is simple enough, just loosen the nut before taking anything else apart.
The oil pump shaft is not the strongest or best made. The shaft is subject to cracking because of the thin metal surrounding the splined drive surface for the gear.
A superior replacement is available. (See reference under NLA parts.) A new gear comes w/ the shaft if you need to change your shaft. Mine broke. If your shaft is good a new sprocket & chain are all you need. DO NOT exceed the torque spec at assembly.
For the price it is not worth taking things apart w/o replacing the OP chain and Sprocket.
The Oil Pump itself:
If the shaft isn't tight, has wear, in the rear half of the pump housing find another pump. It will never develop adequate pressure due to the leakage around the shaft.
Remove and inspect BOTH check balls. Be sure they are clean, round and the springs are not broken/bent.
New gear sets are sometimes available but way too pricy and won't do anything for an otherwise decent pump.
New housings have been NLA for a while. Look for a good used one if a replacement is necessary.
Clear the pick-up screen of all build up. A metal toothbrush (for weld cleanup) works great.
Lap the pump bottom cover flat with a sheet of 360/400 grit wet/dry sandpaper over a sheet of glass/lexan on a suitable bench. Wet it with gas and 20 figure8 strokes will do it.
Do the same with the pump housing. The pump gear end clearance will likely be within spec if the pump is good otherwise. If not a few extra strokes here will fix that. The covers tend to distort between the bolts and leak.
Assembly: pack a slug of chassis grease into the pickup bore to seal it. Pour the pump full of STP and bolt it together. All this is to guarantee that the pump primes immediately and the STP won't run out while you get things put back together. Spin the engine w/ the starter w/ the plugs out until the Oil Pressure Light goes out.
-Dick